Accident often occurs when a tired and/or distracted driver suddenly drives a car into other lanes on a road, a highway, or a freeway. Currently, the technique of using supersonic wave to detect a safe distance between two moving cars has been used to achieve the purpose of driving safety warning. However, for two cars that are moving at high speed, the response time for maintaining a fixed distance between cars is relatively short. Therefore, the safety of driving at high speed is relatively low. In addition, most of the currently available driving safety warning means are of a visual type. That is, the driver has to visually determine the current driving speed and surrounding factors in connection with driving. Such visual-type driving safety warning means are just insufficient for handling unexpected conditions or accidents. Satellite positioning has also been utilized to calculate the safe distance between two moving cars to avoid collision. However, the satellite positioning technique seems not workable in practical application of it to the driving safety warning. In addition, photographic information has also been used to analyze the environmental factors surrounding a car, and image parameters are used to provide the current driving conditions of the car, so as to determine whether the car has been excessively turned or deviated from the original lane.